Development of sucking in term infants from birth to four hours postbirth

The development of the sucking response was investigated in 30 clinically normal infants from 1 or 5 minutes postbirth until their first feeding 4 hours later. Maximum sucking pressures were measured with a research nipple attached to a portable electronic suckometer. Mean suction (negative pressure) began at 5 Torr at birth, peaked at 103 Torr at 90 minutes, and decreased thereafter to 65 Torr at 4 hours. Expression (positive pressure) began at 12 Torr, rose to 29, and decreased to 25. Mean expression pressures correlated with feeding scale scores, r = +. 44(24); p < .025, but suction pressures did not, r = + .26(24); < .1. Normative data were gathered on 10 additional stabilized newborns who had been fed twice successfully. Suction pressures were 96 Torr on Day 1, and 103 Torr on Day 2; expression pressures were 25 and 24 Torr, respectively. These pressures approximate those recorded in newborns between 1 and 2 hours postbirth.